Improvement in wood-screws



UNITED STATES PATENT OEEICE.v

Y .I AMES M. WHITING, OF NEW BEDFORD, MASSACHUSETTS, AND GEORGE F.

WILSON, OF PROVIDENCE, RHODE ISLAND.

IMPROVEMENT IN WOOD-SCREWS.

Specification forming part of Letters Patent No. 19,805, dated March 30, 1858.

.To @ZZ whom it may concern.-

Be it known that we, JAMES MoNRoEWHIT- ING, ofthe city of New Bedford, in the county of Bristol and State of Massachusetts, and GEORGE FRANCIS WILSON, of the city and county of Providence, in the State of Rhode Island, have invented a new and useful Form or Shape for Wood-Screws; and we do hereby declare that the following is a full and exact description thereof, reference being had to the annexed drawings, making a part of this specification, and to the letters of reference marked thereon, in which- Figure 1 is a plan of the screw, and Fig. 2 is a longitudinal cross-section of the same.

The nature of our invention consists in making theupper side of the threads of woodscrews deeper than the under side by taking out more stock from the core or body of the screw on the upper than on the under Side of the thread, thereby greatly increasing the hold of the screw on the Wood into which it is driven, and increasing, in other words, the resistance of the screw to efforts to pull it from its place by direct strain for this purpose under the head.

The peculiar form or shape of that portion of the Screws constructed in accordance with the principles of our invention may be very readily understood by reference to the draw,

ings, Figs. l and 2, in which the same letters refer to like parts. That side of the thread indicated by the letters a a we call the upper side, and that side indicated bythe letters b b we call the under side. By a further inspection at the points indicated by the letters c c c c c, and so on,it will be seen that.

the spaces between the upper and under sides of the threads, so to speak, on the body of the screw are like frustums of cones, the sides of which, if continued, would make more obtuse angles than the body of the screw considered entire, and that the distance from the apex of the thread to the body of the screwr measured ou. the upper side is greater than from the same point on the apex of the thread to the body of the screw measured on the under side of the thread. The strength of the screw is not diminished by this method of construction, for while there is a greater amount of stock than usual removed from the body of the screw next the upper side of the thread there is a correspondiugly-increased amount of stock left on the under and opposite side of the thread.

To enable others skilled in the art to make and use our invention, We will proceed to describe its construction and operation.

To give the peculiar shape (or its equivalent) described above to wood-screws, We make the front and cutting edge o f the chaser or chasers with the requisite bevel or curve, that corner of the chaser next to the upper side of the thread being made to project farther out toward the body of the screw than the corner next to the under side of the thread.

The effect and operation of this method of constructing wood-screws are by the removal of the samek or a given quantity of stock from between the threads to greatly increase the holding-surface of the screw against the wood into which it is screwed beyond the holdingsurface of Wood-screws as ordinarily and heretofore constructed with the upper and under sides of the thread of the same depth.

What we claim as our invention, and desire to secure by Letters Patent, is-

The making of Wood-screws with the upper side of the thread of greater depth than the under side of the thread, substantially as described.

Providence, Rhode Island, January 25, 1853.

JAMES M WRITING. [n s] GEO. F. WILSON. -[L. s.] Y lrVitnesses:

ALFRED ANTHONY, C. T. JAMES. 

